The yarns of pertinence here are highly oriented fully drawn polyester (e.g., polyethylene terephthalate) yarns, e.g., high tenacity industrial polyester yarns of 500 to 2,000 denier. These yarns find application as reinforcing in tires, hoses, belts including conveyor belts and in other articles, e.g., industrial rope, grass catcher bags, geotextiles, tarpaulins, and many other industrial products.
Conventional speed spinning of these yarns involves take-up speeds of 3,000 meters or less. The major portion of melt spun polyester yarns is still made utilizing conventional speed spinning processes.
Spin finish compositions for polyester yarns can be either aqueous emulsions or non-aqueous compositions. Aqueous emulsions can provide good performance for high speed spinning processes and for some conventional speed spinning processes, where multiple stages of yarn drawing are used. However, for single stage drawing processes, aqueous spin finishes usually provide inferior results compared to the non-aqueous spin finishes. Some non-aqueous spin finish compositions consist of mixtures of all oily materials, or the oily mixtures can be dissolved in a solvent system, typically kerosene.